1. Field of the Invention
This invention relates to a lens driving device having a mechanism for performing a focusing operation and a zooming operation, and to an image pick-up apparatus employing this lens driving device.
2. Description of the Related Art
Heretofore, an image pick-up apparatus, such as a video camera, performs a zooming operation and a focusing operation by a structure including a zoom lens within a lens block and a focusing lens outside the lens block. The focusing lens provided outside the lens block is termed a front focusing lens.
Nowadays, the zooming and focusing operations are performed by a structure having the zoom lens and the focusing lens within the lens block. The focusing lens provided within the lens block is termed an inner focusing lens.
Among the systems of focusing with respect to an object with variations in the zoom lens position, there are a so-called manual focusing system in which an operator arbitrarily sets the focus position by a manual operation, and a so-called auto-focusing system in which the focusing operation is performed automatically using a detected output of imaging signals. In the autofocusing system, the operation of correcting the focus position for focusing with respect to the object depending on the distance between the zooming position and the distance up to the object is termed a zoom tracking operation.
In the above imager, if, after manual focusing with respect to the object and securing the focus lens, the state of an iris adjusting the light volume from the object is changed, the focus for the object tends to be deviated.
Moreover, in zoom tracking for automatic focusing, the focus for the object tends to be deviated depending on the state of the iris.